1. Field of the Invention
The present invention relates to a semiconductor device and a method of manufacturing the same and, more particularly, a semiconductor device as an object of thickness reduction and a semiconductor device manufacturing method containing the step of polishing a back surface of a semiconductor substrate.
2. Description of the Prior Art
To reduce a thickness of a semiconductor integrated circuit (LSI) chip is important to the size reduction of the semiconductor device that is constructed by packaging an LSI chip, the three-dimensional packaging technology for stacking the semiconductor devices, etc.
Normally, the method of polishing a back surface of a semiconductor substrate, on which semiconductor elements are formed, is employed as the method of reducing the thickness of the LSI chip.
For example, as shown in FIGS. 1A to 1C, there is such a method that a masking tape 102 is stuck onto one surface of a semiconductor substrate 101, then the other surface (back surface) of the semiconductor substrate 101 is grinding/polished by a grinder 103 to reduce its thickness into a desired thickness, and then the masking tape 102 is peeled off. The masking tape 102 is provided to protect the elements formed on the semiconductor substrate 101 from the mechanical stress caused in grinding/polishing.
As the method of attaching the bump electrodes to the semiconductor substrate to be polished by such method, there are two methods described in the following.
First, as shown in FIG. 2A, in the situation that the masking tape 102 is stuck onto one surface of the semiconductor substrate 101, the other surface of the semiconductor substrate 101 is polished by the grinder 103 to reduce the thickness and then the masking tape 102 is removed from the semiconductor substrate 101. Then, as shown in FIG. 2B, bump electrodes 105 are formed on a pad 104 on one surface of the semiconductor substrate 101.
Second, as shown in FIG. 3, the bump electrodes 105 are formed the pad 104 formed on one surface of the semiconductor substrate 101, then the masking tape 102 is stuck onto one surface of the semiconductor substrate 101 to cover the bump electrodes 105, and then the other surface of the semiconductor substrate 101 is polished, as shown in FIG. 1B.
In this case, the bump electrodes 105 are formed by using resist that is formed after an operation for removing all the masking tape is finished.
Meanwhile, the masking tape employed in grinding/polishing the back surface of the semiconductor substrate is expensive. In addition, the disposal of the masking tape that is peeled off from the semiconductor substrate causes the environmental pollution.
Also, if the bump electrodes are formed on the semiconductor substrate after the grinding/polishing of the semiconductor substrate have been completed, the thinned of the semiconductor substrate is ready to crack in the middle of the formation of the bump electrodes to thus cause the deterioration of the yield.
In contrast, if the bump electrodes are formed on the semiconductor substrate, then the masking tape is stuck on the overall semiconductor substrate, and then the semiconductor substrate is ground/polished, sometimes the semiconductor substrate is cracked due to the stress concentration onto the bump electrodes.
In addition, as described above, there is another problem that a series of operations such as sticking of the masking tape, peeling-off of the masking tape, formation of the bump electrodes, etc. take a lot of times.
It is a first object of the present invention to provide a semiconductor device capable of improving throughput in a series of steps of grinding/polishing of the semiconductor substrate and formation of bump electrodes, and a method of manufacturing the same.
It is a first object of the present invention to provide a semiconductor device manufacturing method capable of preventing crack of the substrate upon grinding/polishing of the substrate on which bump electrodes are formed.
According to the present invention, one surface of the semiconductor substrate is covered with the masking tape that consists of the base material layer and the resist layer coated on this base material layer.
Therefore, if only the base material layer of the masking tape is stripped off after the polishing of the other surface (back surface) of the semiconductor substrate has been finished and then the remaining resist layer is used in patterning as it is, the step of coating the resist onto the semiconductor substrate can be omitted.
Also, according to the present invention, one surface of the semiconductor substrate is covered with the masking tape which consists of the base material layer and the resist layer coated on this base material layer, then the other surface (back surface) of the semiconductor substrate is polished, then the base material layer of the masking tape is stripped off from the masking tape.
Therefore, if the resist pattern used for the bump electrode formation and the wiring formation is formed by exposing/developing the resist layer as it is, time and labor for coating the resist can be omitted and thus the throughput can be improved.
Also, since it is ready to remove the resist layer almost perfectly by the solvent, the upper surface of the semiconductor substrate is never contaminated.
In addition, since the adhesive does not remain on the peeled base material layer unlike the prior art, the base material layer can be re-used and thus an amount of waste product can be reduced, whereby this manufacturing method is useful for the environmental protection.
Further, if the base material layer is formed of material that can block the exposure of the resist layer, the processes required until the peeling-off of the base material layer from the resist layer can be performed in the normal environment. Thus, the operability can be improved.
According to the present invention, prior to the polishing of the back surface of the semiconductor substrate, the flux or the resist is coated between the projection electrodes formed on the opposite side surface and then the masking tape is pasted thereon.
Therefore, in polishing the semiconductor substrate, the pushing force of the masking tape is applied to not only the projection electrodes but also the flux or the resist to scatter, and thus the crack of the semiconductor substrate can be prevented.
Also, in the event that the flux is formed between the projection electrodes, if the masking tape is pasted as it is after the projection electrodes covered with the flux are heated, the number of steps is never increased rather than the prior art.
In addition, in the event that the resist is coated between the projection electrodes, the resist can be cured by baking after the coating and thus the stress applied to the semiconductor substrate becomes uniform.
Further, if the masking tape is pasted on the flux or the resist, the adhesive layer of the masking tape does not remain on the substrate.
According to the present invention, the adhesive layer of the masking tape is projected in the area that corresponds to the peripheral area of the semiconductor substrate.
Therefore, the force applied from the masking tape to the projection electrodes is distributed to the peripheral portion of the semiconductor substrate, and thus the substrate becomes hard to crack.
In addition, a plurality of projection electrodes are formed uniformly in height by the pushing force of the masking tape. In this case, since a pushing level of the masking tape is limited by the projected adhesive layer on the peripheral area, there is no possibility that the height of the projection electrodes is excessively lowered.
According to the present invention, the other surface of the semiconductor substrate is polished in the situation that one surface of the semiconductor substrate is covered with the masking tape, then the masking tape is stripped off in the situation that the go support tape is pasted on the other surface, and then the projection electrodes are formed on one surface.
Therefore, since the semiconductor substrate is reinforced by the support tape, the substrate becomes hard to crack in forming the projection electrodes.